First of all, you need more combo.
Try to do the weird 180 on the rail, and the nosepress 180 on the ground (go to Knowledge base -> SSX series -> SSX3 -> advanced techniques; and then search for them).
Secondly, you need to try your best for a X-X-X (i.e. Triple X-Executioner). Do to that, on each of your Xs, hold the uber a bit shorter, so that it finishes about as soon as the last flip. Then, press any of the shoulder buttons (lightly), which cancels the frames left after the trick. From my own experience, I know the uber trick can't last longer than the flips/spins, or frame cancelling won't work.
Another way to get your monsters faster, is to try to tap as little as possible because every tap still makes the game think you hold it, so it spins slower. It is VERY hard, but try to do your X only with two taps (prewind, then one tap just before each flip ends), and your SA with 1 (prewind, then one tap just before the second flip).
On 0:50 in the video, when you failed a stoneage, you had to do some spins/flips, you could have always added a tweaked grab. Also, judging by the amount of airtime you had left, I think another try for a stoneage would JUST succeed.
Oh yes, judging. As I mentioned your first air, you only did and X-X, with the second one stalled. From now on, try to do your first X, then just quickly estimate how much air you have got left. Right there, with the air time you had and the speed of your tapping, I would have gone for an X-SA-SA.
I think that's all, Keep practicing!
